High sensitivity ionization chamber



March 21, 1961 E. JOHNSON HIGH SENSITIVITY IONIZATION CHAMBER 2 Sheets-Sheet 1 Filed NOV. 22, 1957 NVENTOR.

March 21, 1961 1.. E. JOHNSON 76,443

HIGH SENSITIVITY IONIZATION CHAMBER Filed Nov. 22, 1957 2 Sheets-Sheet 2 FIG. 2.

IN V EN TOR. A 55 L /E E Q/Ofi/A JOM ATrO/GA/E Y8 M Fatented Mar. 211, 1951 HIGH SENSITIVITY IQNIZATION CHAMBER Leslie E. .lohnson, 168th and Kilpatrick Sta, RR. 1, Tinley Park, Ill.

Filed Nov. 22, 1957, Ser. No. 698,227

'6 Claims. (Cl. 313--61) preventing leakage between its inner electrode and the surrounding screen electrode and with means for guarding said inner electrode against currents caused by moving charges from gamma-induced ionization on surfaces of the insulators thereof.

A further object of the invention is to provide an improved ionization chamber especially suited for use under high temperature conditions, said chamber involving relatively inexpensive components, being mechanically rugged in construction, and being provided with improved means for electrically insulating the components thereof from each other, as Well as for sealing said components so that the ionization medium between the inner electrode and its surrounding screen electrode is permanently retained and whereby the chamber is maintained in a stable and efficient operating condition.

A still further object of the invention is to provide an improved ionization chamber having high sensitivity, having high resistance to vibration and shock, and being operable over a wide range of temperatures.

Further objects and advantages of the invention will become apparent from the following description and claims, and from the accompanying drawings, wherein:

Figure 1 is a vertical longitudinal cross sectional view taken through an improved ionization chamber constructed in accordance with the present invention, the chamber being shown divided into two fragmentary segments constituting the forward and rear portions of the chamber and being intended to be placed end-to-end in order to illustrate the entire chamber.

Figure 2 is an end view of the ionization chamber of Figure 1, taken at the end of the chamber having the electrical terminals thereof.

Figure 3 is a transverse vertical cross sectional view taken on the line 3-3 of Figure 1.

Figure 4 is a transverse vertical cross taken on the line 4-4 of Figure 1.

Figure 5 is a transverse vertical cross taken on the line 55 of Figure 1.

Figure 6 is a transverse vertical cross taken on the line 6-6 of Figure 1.

Referring to the drawings, the improved high temperature ionization chamber of the present invention is designated generally at Hand comprises an elongated, generally cylindrical, sealed metal outer container 12 having the circular end wall 13 at one end and being provided at its other end with a circular plug 14 which is sealingly sesectional view sectional view sectional view cured inside a cylindrical lining member 15 provided in the end portion of container 12 remote from the wall 13.

End wall 13 comprises the inwardly extending peripheral flange 16 which is sealingly secured inside the end portion of the container 12. Designated at 17 is a cylindrical lining member, said lining member being of substantial length, as shown in Figure l, and being rigidly secured inside the outer container 12 in abutment with the peripheral edge of the flange 16.

Both of the liner members 15 and 17 are of metal and are secured in sealing engagement with the inside surface of the metal outer container 12. The liner member 15 is formed at its inner end with the annular, inwardly directed flange 18 which is further formed adjacent its inner peripheral edge with a split collar 19 having parallel apertured connecting lugs 20 at the adjacent end portions thereof, said lugs being connected by a clamping screw 21. Clampingly secured in the collar 19 and seating against the inner peripheral portion of the flange i8 is a metal ring member 22 of substantial thickness, said ring member being formed with a central aperture 23.

The lining member '17 is similarly formed at its inner end with an inwardly directed annular flange 24 which is further formed with the inwardly extending split collar 25 provided at its end portions with the opposing fastening lugs 26 which are connected by a clamping screw 27. Clampingly secured in the split collar 25 is a rel"- tively thick metal ring member 28 generally similar to the metal ring member 22,

Metal ring member 28 is provided with the central aperture 29, and secured to said ring member at said aperture is the outwardly extending, flaring collar member 30, said collar member extending toward the end wall 13, as shown in Figure l. A similar collar member 32 is secured in the ring member 22 at its aperture 23, the collar 32 flaring outwardly in width toward the end plug 14, as shown in Figure 1.

Designated at 33 is a tubular metal electrode which is located axially in the container 12 and which extends through the apertures 23 and 29 of the ring members 22 and 23. The electrode 33 extends substantial distances past the partition members 22 and 2S, and is sealingly secured thereto and electrically insulated therefrom. Thus, the left end portion of the electrode 33 has secured thereto an annular sealing collar element 34 which is cup-like in shape and which opposes the collar member 32. A sleeve member 35 of substantial length and of refractory insulating material, such as alumina, or the like, is sealingly secured in the respective sleeve members 32 and 34 surrounding the electrode 33, as is clearly shown in Figure l. The insulating sleeve 35 thus accurately supports the electrode 33 in substantially centered position in the central aperture 23 of the metal partition ring 22.

The right end of the electrode 33 is similarly supported in the metal partition ring 28. Sealingly secured to the end portion of the electrode 33 is an annular cuplike collar member 36 which opposes the flaring collar member 30. An elongated sleeve 37 of refractory insulating material, such as alumina, or the like, has its end portions sealingly secured in the respective collar members 39 and 36, whereby the electrode 33 is supported substantially centrally in the aperture 2? of the ring-like partition member 28.

The electrode '33 is formed adjacent sleeve 35 with a plurality of openings 33. e right end of the tubular electrode 33 is provided with a metal plug 38, for e"- ample, an iron plug, and the left end of the electrode 33, as viewed in Figure 1, is provided with a filling cap 3? terminating in a crimped end portion ill, whereby the electrode 33 is hermetically sealed after the ionization chamber has been filled with a suitable ionizable gas.

Respective metal guard sleeves 41 and 4,2 are rigidly secured to the respective partition rings 22 and 28 and extend inwardly substantial distances therefrom, coaxially with and spaced from the tubular. inner electrode 33. The metal guard sleeves 41 and 42 are electrically connected through the metal rings 22 and 28 and the metal liner members 15 and 17 to the metal outer container 12.

Designated at 43 is a generally cylindrical, elongated metal inner container which is coaxially arranged with the electrode 33 and which surrounds the intermediate portion of said electrode, the opposite end portions of the container 43 extending outwardly beyond the inner end portions of the guard sleeves 41 and 42, whereby the end portions of the outer container 4-3 overlap the inner end portions of said guard sleeves, as is clearly shown in Figure l. The inner container 43 is insulated from and sealingly connected to the respective partition rings 22 and 28. Thus, the partition rings 22 and 28 are provided with the inwardly flaring peripheral collar elements l4 and 4-5 which are rigidly secured thereto. Rigidly secured to the inwardly extending peripheral flanges 46 and 4'7 formed in the inner container 43 are respective outwardly flaring collar members 48 and 49 which respectively oppose the collar members Maud 45. Designated at 54) and 51 are respective elongated sleeve members of refractory insulating material, such 7 as alumina, or the like, which are sealingly secured within the respective pairs of opposing collar members 44, 318

and 49, 45. Thus, the end portions of the refractory insulating sleeve 50 are sealingly secured respectively in collar members '44 and 48, and the end portions of the refractory insulating sleeve 51 are respectively sealingly secured in the collar members 3-9 and 45. Therefore,

7 the inner container 43 is supported concentrically around the inner electrode 33 and is electrically insulated therefrom by the elongated refractory insulating sleeves 56, '51. However, the portions of the electrode 33 contained within the insulating sleeves t) and 51 are eflectively guarded against the elfects of gamma-induced surface currents on the insulating sleeves by the guard sleeves 41 and 42, said guard sleeves also preventing leakage of charge or leakage current between electrode 33 and the respective ends of the metal inner container 43.

The enclosure defined within the inner container 43 and the space adjacent its end portions enclosed by the respective refractory insulating sleeves 50 and 51, as well as the space within the inner electrode 33, is filled with a suitable ionizable gas sensitive to the presence of radioactive material, such as boron fluoride employing the B isotope of boron. The high sensitivity of this gas (B 1 makes it highly suitable for the detection of neutrons and of other radiation associated with the radioactive material. 1

The outer container 12 is filled with a suitable inert the inner container 43 and supporting means therefor. This acts to protect the entire inner assembly against oxidation, particularly at high temperatures; said inertgas (which is substantially at the same pressure'as the gas in the inner container 43) alsoacts as a pressure-balvoltage terminal E2. is sealinglysecuredaxially'in a generally cylindrical insulating block 54 of refractory in-v sulating material, such as alumina or the like, the terminal 52 being "provided with 'a bonding. sleeve 55 which provides a gas tight seal between the terminal 52 and the refractory insulating block 54. .The, block'54 in gas, such as dry nitrogen, or the like, which surrounds f turn is sealingly secured to the plug disc 14 by a flared connecting collar 56 which is sealingly and rigidly secured at one end thereof in the disc 14 concentrically around the aperture 5-3 and which receives and is sealingly fastened to the end portion of the insulating block 54; A guide sleeve 57 is seemed to the plug 14 concentrically around the terminal prong 52 at the outer portion thereof, extending beyond the end of the terminal prong 52, as shown in Figure l, to act as a guide means for aiding a terminal sleeve from a suitable high voltage source to be conductively engaged with the prong 5*2. Said terminal sleeve forms part of a conventional electrical connector and is well known per se.

Designated at 58 is a signal terminal prong which is secured longitudinally in the end portion of the outer container 12 and which is sealingly, insulated therefrom by an elongated sleeve member 59 of refractory insulating material, such as alumina or the like. As shown, the terminal prong 58 extends axially through an aperture 60 formed in the plug member 14 and has one end thereof centrally secured in an annular cup-like member 61 facing the aperture -60. A flaring collar member 62 is sealingly secured to the plug member 14 in the aperture 60, opposing the cup member 61. The insulating sleeve 59 is sealingly secured at its ends respiectively in the collar member 62 and the plug member 6 Securedto the plug member 14 is an externally threaded, outwardly projecting guide sleeve 63 which coaxially surrounds the signal prong 58 and which is adapted to be engaged by a conventional connector including a contact sleeve engageable on the prong 58, for transmitting the signal from the ionization chamber to a suitable electrometer or other receiving means.

The terminal member 58 is formed with a reduced inner end portion 64 which is connected by a Wire 65 to a contact collar 66 clampingly engaged on the end portion ofthe hollow inner electrode 33 between the cap 39 and the cup-like collar member 34, as shown in Figure l. The inner end of the high voltage prong 52 is connected by a wire 66 to the peripheral end flange 46 of the inner container 43. 7

As is well understood to those skilled in the art, the outer container 12 is grounded and the high voltage source has one terminal thereof likewise grounded. The other terminal thereof is connected to the high voltage prong 52, whereby the inner container 43 is placed at a high potential with respect to ground.

Obviously, the outer container 12 may be maintained at any potential other than ground potential, if so desired, said'potential being this employed as a reference potential with respect to the relatively high potential applied to the inner container 43.

In the presence of radioactive material, such as, for

example, neutrons, or the like, ionization will occur in the boron fluoride contained in the inner container 43, whereby a signal will develop between the inner electrode 33 and the outer container 12, which signal will be available at the signal terminal prong 58. As above explained, a suitable output conductor may be connected to the signal terminal 58 to transmit the signal to a suitable e'l'ectrometer or other signal-receiving means.

The end plug 14 of the chamber is provided with a suitable filling tube 70 through which the dry nitrogen or other inert gas may be supplied'to the interior of the chamber, the filling tube 70 being subsequently sealed after the gas has been admitted'into the chamber, for example, by crimping same, as shown at 71, and sealing the tapered end of the crimped portion with suitable hard solder; l

As above explained, the guard sleeves 42 and Mad to guard the inner electrode 33 agai-ns-tthe eflects of currents caused by moving charges from gamma-induced ionization on theisurfaces of the'insulating' sleeves 54) and 5 1. 7

acrea e All of the metallic joints in the ionization chamber are preferably copper or silver alloy brazed to provide an eficient seal and to resis relatively high temperatures. The sealing means employed throughout preferably comprises a highunelting point, high strength alloy, such as a copper-silver alloy, or the like. In a typical embodiment of the invention the ionization chamber could be operated efliciently at temperatures higher than 600 F. An operating voltage or" 1500 volts negative was applied to the high voltage terminal 52. This provided substantial sensitivity both to neutrons and to gamma radiation.

While specific embodiment of an improved high sensitivity ionization chamber has been disclosed in the foregoing description, it will be understood that various modifications within the spirit of the invention may occur to those skilled in the art. Therefore, it is intended that no limitations be placed on the invention except as defined by the scope of the appended claims.

What is claimed is:

1. An ionization chamber comprising an elongated metal, sealed outer container, a metal electrode member extending longitudinally through said outer container, respective centrally apertured metal transverse partition members secured in said outer container and receiving the respective opposite end portions of said electrode member, rigid insulating means sealingly and supportingly connecting said opposite end portions to said partition members, respective metal guard sleeves secured to said partition members and extending inwardly towards each other and axially surrounding the portions of said electrode member adjacent said partition members, an elongated metal inner container surrounding the intermediate portion of said electrode member and overlapping said guard sleeves, rigid insulating means sealingly and supporti-ngly connecting the opposite ends of said inner container to said partition members, said inner container, insulating means, and partition members being constructed and arranged to define a sealed inner compartment surrounding said electrode member and extending between the opposite end portions thereof, ionizasie material sealed in said inner compartment and isolated from the outer container, a pair of terminal members extending through one end wall of said outer container, insulating means sealingly securing said terminal members to said one end wall, respective conductors electrically connecting the terminal members to said electrode member and said inner container, and inert material in the outer container substantially at the same pressure as the ionizable material in the inner compartment and acting as a pressure-balancing means to counteract pressure changes with temperature of the :ionizable material in said inner compartment.

2. An ionization chamber comprising an elongated metal, sealed outer-container, a metal electrode member extending longitudinally and axially through said outer container, respective centrally apertured metal transverse partition members secured in said outer container and receiving the respective opposite end portions of said electrode member, rigid sleeve-lilte insulating means sealingly and supportingly connecting said opposite end portions to said partition members, respective metal guard sleeves secured to said partition members and extending inwardly towards each other and axially surrounding the portions of said electrode member adjacent said partition members, an elongated metal inner container axially surrounding the intermediate portion of said electrode mernher and overlapping said guard sleeves, rigid sleeve-like insulating means sealingly and supportingly connecting the opposite ends of said inner container to said partition members, said inner container, insulating means, and partition members being constructed and arranged to define a sealed inner compartment surrounding said electrode member and extending between the opposite end portions thereof, iouizable material sealed in said inner compartment and isolated from the outer container, a pair of terminal members extending through one end wall of said outer container, insulating means sealingly securing said terminal members to said one end wall, respective conductors electrically connecting the terminal members to said electrode member and said inner container, and inert material in the outer container substantially at the same pressure as the ionizable material in the inner compartment and acting as a pressure-balancing means to counteract pressure changes with temperature of the ionizable material in said inner compartment.

3. An ionization chamber comprising an elongated metal, sealed outer container, a metal electrode member extending longitudinally and axially through said outer container, respective centrally apertured metal trans- V verse partition members secured in said outer container and receiving the respective opposite end portions of said electrode member, rigid sleeve-like insulating means sealingly and supportingly connecting said opposite end portions to said partition members, respective metal guard sleeves secured to said partition members and extending inwardly towards each other and axially surrounding the portions of said electrode member adjacent said partition members, an elongated metal inner container axially surrounding the intermediate portion of said electrode member and overlapping said guard sleeves, rigid sleevelike insulating means sealingly and suppontingly connecting the opposite ends of said inner container to said partrtion members, said inner container, insulating means, and partition members being constructed and arranged to define a sealed inner compartment surrounding said electrode member and extending between the opposite end portions thereof, ionizable material sealed in said inner compartment and isolated from the outer container, a pair of elongated terminal members extending longitudinally through one end wall of said outer container, insulating means surrounding said terminal members, means connecting said last-named insulating means to said terminal members and to said one end wall and sealingly securing said terminal members to said one end wall, respective conductors in said outer container electrically connecting the terminal members to said electrode member and said inner container and inert material in the outer container substantially at the same pressure as the ionizable material in the inner compartment and acting as a pressure-balancing means to counteract pressure changes with temperature of the ionizable material in said inner compartment.

4. An ionization chamber comprising an elongated metal, sealed outer container, a tubular metal electrode member extending longitudinally and axially through said outer container, respective centrally apertured metal transverse partition members secured in said outer container and receiving the respective opposite end portions of said electrode member, rigid sleeve like insulating means sealingly and supportingly connecting said opposite end portions to said partition members, respective meta guard sleeves secured to said partition members and extending inwardly towards each other and axially surrounding the portions of said electrode member adjacent said partition members, an elongated metal inner container axially surrounding the intermediate portion of electrode member and overlapping said guard sleeves, rigid sleeve-like insulating means sealingly and supportingly connecting the opposite ends of said inner container to said partition members, said inner container, sleeve-like insulating means and partition members being constructed and arranged to define a sealed inner compartment surrounding said electrode member and extending betwe n the opposite end portions thereof, a pair of elong terminal members extending longitudinally through one end wall of said outer container, insulating sleeves surrounding said terminal members, means connecting said last-named insulating sleeves to said terminal members and to said one end wall and sealingly securing the t=.-

minal members to said one end wall, respective conduc- I tors in said outer container electrically connecting the terminal members to said electrode member and said inner container, a quantity of ionizable gas sealed in said inner compartment and isolated from the outer container, and inert gas in the outer container substantially at the same pressure as the iouizable gas in the inner compartment and acting as a pressure-balancing means to counteract pressure changes with temperature of the ionizable gas in the inner compartment.

5. An ionization chamber comprising an elongated metal, sealed outer container, a tubular metal electrode member extending longitudinally and axially through said outer container, respective centrally apertured metal transverse partition members secured in said outer container and receiving the respective opposite end portions of said electrode member, rigid sleeve-like insulating means sealingly and supportingly connecting said opposite end portionsto said partition members, respective metal guard sleeves secured to said partition members and extending inwardly towards each other and axially surrounding the portions of said electrode member adjacent said partition members, an elongated metal inner container axially surrounding the intermediate portion of said electrode member and overlapping said guard sleeves, rigid sleeve-like insulating means sealingly and supportingly connecting the opposite ends of said inner container to said partition members, said inner container, partition members and sleeve-like insulating means being constructed and arranged to define a sealed inner compartment surrounding said electrode member and extending between said opposite end portions of the electrode member, a pair of elongated terminal members extending longitudinally through one end wall of said outer container, insulating sleeves surrounding said terminal members, means connecting said last-named insulating sleeves to said terminal members and to said one end wall and sealingly securing said terminal members to said one end wall, respective conductors in said outer container electrically connecting the terminal members .to said electrode member and said inner container, a quan: tity of ionizablc gas sealed in said inner compartment and isolated from the outer container, said gas comprising a compound including an isotope of boron, and inert gas in the outer container substantially at the same pressure as the ionizable gas in the inner compartment and acting as a pressure-balancing means to counteract pressure changes with temperature of the ionizable gas in the inner compartment.

6. An ionization chamber comprising an elongated metal, sealed outer container, a tubular metal electrode member extending longitudinally and axially through said outer container, respective centrally apertured metal transverse partition members secured in said outer container and receiving the respective opposite end portions of said electrode member, rigid alumina insulating sleeves sealingly and supportingly connecting said opposite end portions to said partition members, respective metal guard sleeves secured to said partition members and extending inwardly towards each other and axially surrounding the portions of said electrode member adjacent said partition members, an elongated metal inner container axially surrounding the intermediate portion of said electrode member and overlapping said guard sleeves, rigid alumina insulating sleeves sealingly and supportingly connecting the opposite ends of said inner container to said partition members, said inner container, partition members and insulating sleeves being constructed and arranged to define a sealed inner compartment surrounding said electrode member and extending between said opposite end portions of the electrode member, a pair of elongated terminal members extending longitudinally through one end wall of said outer container, alumina insulating sleeves surrounding said terminal members, means connecting said last-named insulating sleeves to said terminal members and to said one end wall and sealingly securing said terminal members to said one end wall, respective conductors in said outer container electrically connecting the'terminal members to said electrode member and said inner container, a quantity of ionizable gas sealed in said inner compartment, and a quantity of inert gas sealed in said outer container surrounding said inner compartment and isolated from the gas in said inner compartment, said inert gas being substantially at the same pressure as the ionizable gas in the inner compartment and acting as a pressure-balancing means to counteract pressure changes with temperature of the ionizable gas in the inner compartment.

References Cited in the file of this patent UNITED STATES PATENTS 

